1. Field of the Invention
The present invention relates to a recording apparatus and a predischarge control method. More particularly, the invention relates to a recording apparatus that records using an ink jet recording head, and a predischarge control method.
2. Related Background Art
The ink jet recording method is utilized for various kinds of printers, copying machines, facsimile equipment, and others, because it has such advantages as lower noises, lower running cost, easier downsizing of the apparatus, and easier recording of images in colors.
The recording apparatus that adopts this method records on a recording medium, such as paper, cloth, non-woven textile, OHP film, by discharging minute ink droplets from fine discharge ports of the ink jet recording head (hereinafter, referred to as a recording head). As a result, if the recording head is in a state where it is at rest continuously without any recording operation and does not discharge ink for a long time, ink in the ink discharge ports (hereinafter, referred to as discharge ports) is evaporated and dried eventually, hence excessively viscose ink or solidified ink being allowed to clog discharge ports to bring about dot mis-alignment (the phenomenon that ink discharge direction may change) or defective discharges. Here, therefore, in order to eliminate such drawback, the ink jet recording apparatus is provided with recovery means for performing recovery process to recovery the discharge condition of ink.
The ink jet recording apparatus (hereinafter, referred to as a recording apparatus) adopts the structure given below in order to solve the problems of dot mis-alignment and defective ink discharges due to the evaporation and drying of ink in discharge ports.
At first, the recording operation is at rest, a cap covers the discharge port surface of a recording head where discharge ports are formed, thus preventing ink in the discharge ports from being evaporated and dried. Should the viscosity of ink increase so as to allow ink to adhere to the discharge ports firmly with the defective discharges that may occur or should foreign substances adhere to the discharge port surface, the suction pump, which is connected to the inside of the cap, sucks overly viscous ink in the discharge ports or the foreign substances adhering to the discharge port surface to expel them. In this manner, recovery is executed to the normal discharge condition (this is referred to as a suction recovery).
Also, for the recording operation of the recording apparatus that adopts on-demand type ink jet recording method, all the discharge ports provided for one recording head are not necessarily used at all the time, and there exist some unused nozzles that are not used for a certain time or more. Also, for the color recording apparatus, which is provided with plural recording heads corresponding to each color ink, a certain recording head is not used entirely in some cases due to the absence of recording data to be transmitted.
Further, for the serial scan type where the carriage, on which heads are mounted, scans for recording, the carriage is required to scan or stop for a continuously long time in a state where the discharge port surface of a certain head, which is not in used, is uncapped, ink in the discharge ports, from which no ink discharges take place, is evaporated and dried. As a result, the ink discharge performance is degraded, hence inviting the degradation of quality of recorded images eventually.
To prevent such phenomenon, it is generally practiced for the recording apparatus to discharge ink at a designated location at intervals of certain time without regard to recording data so that ink in each nozzle is exhausted for replacement with flesh ink. In this manner, ink discharge condition is maintained appropriately at all the time. The ink discharge operation of the kind is called xe2x80x9cpredischargexe2x80x9d.
Ink discharged as predischarges is directed to the location defined as the predischarge position, which is arranged in the cap of the recovery unit or arranged separately so as not to allow such ink to splash onto a recording medium or the interior of the recording apparatus to stain it. Lastly, then, ink discharged in such a manner is retained in a waste ink tank. The technique with which to discharge ink in the cap is disclosed in the specifications of Japanese Patent Application Laid-Open No. 59-7053 and Japanese Patent Application Laid-Open No. 04-52219, for example.
In recent years, for the enhancement of quality of recorded images, there has been proposed technique such as to improve the water-resistance by making ink insoluble on a recording medium or prevent spreading thereof on a recording medium with discharge of a specially treated recording capability enhancement liquid (hereinafter, referred to as processing liquid), besides ink, thus improving the quality of recorded images. For the recording apparatus that adopts such technique as this, plural receiving portions are arranged on positions apart from each other to receive ink and processing liquid when predischarges are performed. However, the provision of such plural receiving portions for predischarged ink and processing liquid leads to making the apparatus larger inevitably. Here, therefore, there has been proposed the utilization of the interior of cap as the predischarge position for the purpose of making the recording apparatus smaller.
Also, in recent years, it has been demanded to record images on an elongated recording sheet (banner paper) like a drop curtain. When recording on such an elongated recording sheet, the frequency of predischarges increases during recording operation as compared with recording on a sheet of regular size (A4, legal size, or the like) such as a usual copying sheet. The amount of ink used for predischarges increases accordingly. With the structure arranged to enable predischarges to be performed in the cap, the ink, which is pooled in the cap, should be sucked for removal appropriately (hereinafter, referred to as idle suction), and if the idle suction operates during recording operation, the reduction of throughput is invited.
To solve this problem, there has been proposed in the specification of Japanese Patent Application Laid-Open No. 03-234638 an idle suction of ink remaining in the cap each time when one-page portion of recording is completed, while performing predischarges in the cap.
Also, in the case of serial type recording apparatus where the carriage that has recording head mounted thereon reciprocates in the direction at right angles to the conveying direction of a recording medium, such as paper, it is generally arranged to provide the driving source (motor or the like) that drives mainly the carriage, the driving source that conveys the recording medium, and the driving source that drives recovery means for executing the recovery process to recovery the discharge condition of the recording head, and then, the structure is prepared to drive each of them as required. In recent years, however, along with the downsizing of recording apparatus, there have been made available many kinds of apparatuses that adopt the structure arranged to share a driving source for use of the conveyance of recording medium and the performance of recovery means from the viewpoint of cost down, and use such driving source by switching for the purpose. In the specification of Japanese Patent Application Laid-Open No. 01-82962, for example, it has been disclosed that a recording apparatus is arranged to use a motor dually as the motor to drive the suction pump for performing recovery process of the recording head and as the one to convey paper sheet serving as a recording medium.
However, the adoption of the structure, which is arranged to execute the conveyance control and recovery control by driving one and the same motor as the conventional example described above, has encountered the problems given below in some cases.
For example, in a state where recoding mediums (recording sheets, for instance) are set on a recording apparatus, the performance of recovery process that is intended to do then allows the recording sheet to be conveyed along with the recovery operation, because one and the same motor used for both operations. Therefore, the position of the recording sheet is displaced to make it impossible to continue recording images in good condition, or in some cases the recording sheet is put outside the conveyance mechanism on the way of recording. In order to solve such problems, it is necessary to effectuate control so that any recovery operation is not executed or any execution thereof is not allowed during the recording operation or while the recording sheet resides within the range of the conveyance mechanism.
Also, when recording is performed on an elongated recording sheet described earlier by use of such recording apparatus as this, the amount of ink used for predischarges becomes large, while it is made impossible to actuate the idle suction on the way of recording operation. Under such circumstances, the execution of predischarges results in overflowing of ink in the cap, and there is a fear that the interior of the recording apparatus is stained eventually. To solve this problem, there is a disclosure in the specification of Japanese Paten Application Laid-Open No. 10-278299 to the effect that predischarge control means is provided to prohibit predischarge to the cap when the amount of ink in the cap becomes beyond a designated amount. However, if predischarge to the cap is prohibited, there unavoidably exist the discharge ports that remain unused for a long time. As a result, the degradation of quality of recorded image is invited eventually. Also, the degradation of quality of the kind may exert influence not only on images currently recorded, but also, on those to be recorded next in some cases.
It is an object of the present invention to provide a recording apparatus capable of efficiently performing the predischarge that discharges ink, which does not contribute to image recording, from the recording head, and also, capable of reducing the contamination inside the recording apparatus.
It is another object of the invention to provide a recording apparatus that records images on a recording medium by use of an ink jet recording head to discharge ink from discharge ports comprises a cap covering the discharge port surface of the ink jet recording head having discharge ports formed thereon, being capable of receiving ink discharged from the discharge ports; idle suction means for exhausting ink received by the cap to the outside; predischarge means for pre-discharging ink from the ink jet recording head to the inside of the cap at designated time intervals aside from recording operation; accumulating means for accumulating the amount of ink consumption by the predischarge; first comparison means for comparing the amount of ink consumption accumulated by the accumulating means with a first threshold value per predischarge; first predischarge control means for controlling to reduce the amount of ink discharge for predischarge to follow in accordance with the comparison result provided by the first comparison means; second comparison means for comparing the amount of ink consumption accumulated by the accumulating means with a second threshold value larger than the first threshold value per predischarge of the amount of ink discharge reduced by the first predischarge control means; predischarge prohibition means for controlling to prohibit predischarge operation in accordance with the comparison result of the second comparison means; and second predischarge control means for controlling to resume predischarge to follow after the completion of recording operation in accordance with the period of time defined by the predischarge operation prohibition means for prohibiting predischarge operation, and to increase the amount of ink consumption for the predischarge.
Further, for the recording apparatus, it is desirable to provide idle suction control means for controlling to drive the idle suction means to perform idle suction operation after the completion of recording operation, and then, to control idle suction control means so that idle suction means is driven to perform idle suction operation prior to the start of recording operation in accordance with the comparison result of the first comparison means.
It is still another object of the invention to provide a predischarge control method used for a recording apparatus provided with an ink jet recording head, a cap covering the discharge port surface of the ink jet recording head having discharge ports formed thereon, being capable of receiving ink discharged from the discharge ports, predischarge means for pre-discharging ink from the ink jet recording head to the inside of the cap at designated time intervals aside from recording operation, and idle suction means for exhausting ink received by the cap to the outside, which comprises the accumulating step of accumulating the amount of ink consumption by the predischarge; first comparison step of comparing the amount of ink consumption accumulated in the accumulating step with a first threshold value per predischarge; first predischarge control step of controlling to reduce the amount of ink discharge for predischarge to follow in accordance with the comparison result in the first comparison step; second comparison step of comparing the amount of ink consumption accumulated in the accumulating step with a second threshold value larger than the first threshold value per predischarge of the amount of ink discharge reduced in the first predischarge control step;
predischarge prohibition step of controlling to prohibit predischarge operation in accordance with the comparison result in the second comparison step; and second predischarge control step of controlling to resume predischarge to follow after the completion of recording operation in accordance with the period of time defined in the predischarge operation prohibition step of prohibiting predischarge operation, and to increase the amount of ink consumption for the predischarge.
It is a further object of the invention to provide a predischarge control method used for a recording apparatus provided with an ink jet recording head and a cap covering the discharge port surface of the ink jet recording head having discharge ports formed thereon, which comprises the predischarge step of pre-discharging ink form the discharge ports of the ink jet recording head into the cap aside from the recording operation; accumulating step of accumulating the amount of ink consumption by the predischarge; compassion step of comparing the amount of ink consumption accumulated in the accumulating step; and predischarge control step of controlling to reduce the amount of ink discharge for predischarge to follow in accordance with the comparison result in the comparison step.
In accordance with the present invention, the predischarge can be performed efficiently and flexibly corresponding to the recording condition, while eliminating any possibility that ink, which resides in the cap by predischarge, is not allowed to overflow from the cap, hence producing an effect that the interior of the recording apparatus is prevented from being contaminated with ink.